a, Schematized diagram of stepwise differentiation strategy for generation of ureteric bud and collecting duct organoids. b, Immunofluorescent (IF) staining of monolayer cultures at day 1 revealed efficient induction of TBXT-expressing mesendodermal progenitor cells. c, Gene expression analyses by qPCR revealed dynamic down- and up-regulation of pluripotency (NANOG) and primitive streak (TBXT) markers, respectively, after one day of induction. Following two subsequent days of exposure to IM-inducing factors, TBXT was repressed and there was robust activation of PAX2, PAX8, and GATA3. n=3 independent biological replicates per timepoint. d, IF staining of day 3 monolayer cultures demonstrated a high proportion of cells with co-expression of pronephric IM genes PAX2, PAX8, GATA3, LHX1, and HOXB7. e, Quantification of staining for GATA3 and PAX2 represented on histogram revealed a high efficiency of differentiation into pronephric IM fate. n=7 quantified fields from 3 independent biological replicates. f, Following aggregation of IM cells at day 3, the resulting structures underwent stereotypic morphogenetic events characterized in the timecourse of stereomicrographs and fluorescent imaging using GATA3-mScarlet reporter. By day 7, the GATA3+ cells arranged into a dense sphere that excluded a minority population of negative cells. g, IF staining of sections of nephric duct spheres at days 4 and 7 demonstrated maintenance of expression of PAX2, PAX8, and GATA3. h, UMAP representing scRNA-seq of cells isolated from spheres at day 7, which demonstrated the presence of both nephric duct (clusters 2 and 3) and stromal (clusters 0 and 1; PDGFRA+) lineages. i, The majority of cells at day 7 expressed the nephric duct leader fate marker ALDH1A3 with low levels of the mature epithelial marker CDH1. Scale bars 100 μm (b and d), 50 μm (f, g and i). Column and error bars represent mean and standard deviation, respectively.